Session MC - Micro-Fluid Dynamics IX.
MIXED session, Tuesday afternoon, November 23
Grand III, Westin Seattle
The characterization of flows containing macromolecules is critical for the optimal design of microfluidic systems for biochemical analyses. Digital Particle Image Velocimetry (DPIV) is used to measure the velocity fields of DNA-laden flow through an abrupt planar contraction, which is a canonical microfluidic structure and a viscoelastic benchmark. In this microfluidic structure the DNA solution is subjected to high spatial gradients and convective acceleration near the channel contraction. The spatially developing flow consists of regions of elongation along the channel centerline and shear at the walls. The velocity fields for flows of \lambda-DNA solutions are characterized for DNA concentrations in the dilute and semi-dilute range. The molecular contour length L approaches the device length scale D (L/D\sim0.3) for these flows. Vortex enhancement is observed in the corners of the contractions for increasing Deborah number (0.1<De<10). Deviations from Newtonian flow fields brought about by the viscoelastic fluid rheology, concentration effects, and conformational changes of the molecules are assessed.